(I knew I was missing something) I don't recommend it either for people as well. It works well if they have a lot of body fat to lose (~20% for men, ~35% for women), but the benefits begin to diminish when there's less body fat to retrieve. For people who want to get that "ripped" look (which is almost everyone), the amount of effort is too much to prevent catabolism of muscle (a higher ratio of protein to fat is burned for energy, and a high amount of free amino acids (protein) is needed to prevent the need to catabolize skeletal muscle for it)

However, I do like the "zone" dieting as it limits the amount of insulin produced by limiting the amount of carbs to less than 100g, which can be 25-30% of their overall nutrient intake for carbs. With a bit of glucose, it's just enough to provide a quick source of sugars without having to go into ketosis, which can be a problem when dieting to single-digit body fat%.